I recently upgraded to 10.4 and I have been having an issue with my dashboard formatting when I use a high DPI monitor. When I design a dashboard I include my filters in a horizontal container across the top and whenever I open the dashboard with a high DPI monitor everything looks great except for the filters. It is like the height for that container gets set to 1 and in order to see the filters again I either have to make it floating and then place it back or grab the container and move it to a different spot on the dashboard. Even after saving if I open the workbook on a non DPI monitor and then go back to the DPI one the issue repeats itself.
Take a look at this article:
Tableau can look over-scaled or misaligned due to the way 10.4 interacts with High DPI monitors.
Hopefully some the information in this article is helpful!